Automatic brake and steering system and method for a vehicle

ABSTRACT

An automatic brake and steering system and method for a vehicle contains a sensor unit for sensing vehicle state and characteristic variables, and ambient conditions. Furthermore, a control unit and actuator devices are provided for setting the vehicle brake system and/or the vehicle steering system. In order to be able to carry out automatic avoidance maneuvers with maximum safety, an avoidance route is determined if there is an obstacle in the path of the vehicle. Thereby, if there is a further obstacle on the avoidance route, the strategy for determining the avoidance route is applied once more. If it is not possible to find a collision-free avoidance route, that route on which the difference between the remaining braking distance and the remaining distance from the obstacle is smallest is selected.

BACKGROUND OF THE INVENTION

The present invention relates to an automatic brake and steering systemfor a vehicle. More particularly, the present invention relates to sucha system having a sensor unit for sensing vehicle state variables andvehicle characteristic variables as well as for sensing ambientconditions, having a control unit in which actuation signals can begenerated as a function of the vehicle state variables and the ambientconditions, it being possible to feed actuation signals to actuationdevices in the vehicle in order to set the vehicle brake and the vehiclesteering system, the distance between the current position of thevehicle and the obstacle as well as the expected braking distance inorder to stop the vehicle being determined when there is an obstacle inthe path of the vehicle, and an avoidance path for driving around theobstacle being automatically driven along in accordance with a storedavoidance strategy.

DE 40 39 005 A1 discloses a control system for a vehicle which comprisesa sensor arrangement, a central control unit and a multiplicity ofactuator devices for various assemblies of a vehicle which influence thestate of the vehicle. The sensor arrangement registers activitiescarried out by the driver, in particular a braking and a steeringactivity of the driver, and vehicle state variables, for example thespeed of the vehicle and the wheel speeds are determined. The determinedsignals are processed, in accordance with a stored calculation rule, inthe control unit in which actuation signals are generated which are fedto the actuator devices of the vehicle assemblies in order to manipulatethe state of the vehicle. The assemblies to be influenced comprise,inter alia, the vehicle gearbox, a steering control device and a brakedevice.

This known control system has the disadvantage that only activities ofthe driver and the vehicle state can be sensed but not processes andstates which take place or exist outside the vehicle. It is thereforenot possible to sense possible obstacles on the carriageway and to takemeasures to avoid collisions. The control system described in DE 40 39005 A1 cannot be used to implement automatic, autonomous driving.

WO 90/02985 A1 discloses a method and a device for automaticallyavoiding collisions for vehicles. The device and method includepredictive sensing of an obstacle, the collision-avoiding avoidancemaneuver being carried out when an obstacle is detected. When there isan object, an avoidance path is calculated in accordance with anavoidance strategy stored in the control unit. The actuator device forthe steering is acted on in such a way that the vehicle follows theavoidance path and drives around the obstacle.

Although the brake and steering system described in WO 90/02985 A1enables collisions with obstacles to be avoided in a predictive way bycarrying out braking maneuvers and avoidance maneuvers, it isdisadvantageous that the avoidance strategy does not contain anyalternatives if further unexpected obstacles arise during the avoidancemaneuver.

SUMMARY OF THE INVENTION

The present invention is based on an object of providing a vehiclesystem with which automatic avoidance maneuvers can be carried out withthe highest possible degree of safety.

This problem has been solved according to the present invention byproviding that, in the event of a further obstacle lying in theavoidance path, the avoidance strategy is applied once more in order tocalculate an alternative avoidance path such that, in the event of itbeing impossible to find a collision-free avoidance path, that avoidancepath on which the difference between the remaining braking distance andthe remaining distance from the obstacle on the respective avoidancepath is the shortest is selected form a plurality of alternatives.

In the novel automatic brake and steering system according to thepresent invention, at least in the event of a further obstacle beingdiscovered in the avoidance path, an alternative avoidance path iscalculated once more in order to obtain an alternative route for drivingaround the further obstacle. If the alternative route makes it possibleto drive around the obstacle without danger, the assemblies of thevehicle have corresponding actuation signals applied to them in order tofollow the alternative route. However, if the alternative route does notpermit hazard-free avoidance, according to a stored optimizationstrategy, that avoidance route on which the expected damage is smallestis advantageously selected. Expediently, the difference between theremaining braking distance and the remaining distance from the obstacleis determined—starting from the current position of the vehicle—for eachdetermined avoidance route, and that avoidance route on which thedifference between the braking distance and the distance is smallest isadopted.

As an alternative to the optimization strategy of the minimum distancebetween the remaining braking distance and the remaining distance fromthe obstacle, it is, however, also contemplated to apply otheroptimization criteria. It may, in particular, be expedient forperipheral conditions which result from the topology of the surroundingarea to be taken into account in the determination of the avoidanceroute. Such peripheral conditions may be defined, for example, bydetermining the absolute position of the vehicle by aposition-determining system while taking into account the topology knownfrom an electronic road map.

On the basis of the avoidance strategy of the present invention, it isensured that, if a collision cannot be avoided, that route on which thevehicle has the smallest remaining braking distance on reaching theobstacle is selected so that the speed of the vehicle is also minimizedat the time of the impact and the damage is also correspondingly kept assmall as possible.

In one expedient embodiment, additional peripheral conditions in thesurroundings, which conditions can be sensed by the sensor unit of thebrake and steering system, are taken into account. These additionalperipheral conditions which describe, in particular, characteristicfeatures of the surroundings are included in the avoidance strategy inorder to ensure that the avoidance route of the vehicle does not lead togreater damage than if the vehicle remained on the previous route. Byvirtue of the formulation of the peripheral conditions, it is possibleto take into account additional safety-related aspects in the selectionof the route. For example, it is thus contemplated for the obstacleswhich can be sensed by the sensor unit to be divided into differentcategories, it being also possible to define categories of obstacleswith which a collision can be avoided unconditionally. This relates inparticular to persons on the carriageway and/or on the avoidance route.

It is also contemplated to take into account as a peripheral conditionthe fact that the avoidance route must not lead onto the oncomingcarriageway. This applies in particular to the case in which, whenperforming an avoidance maneuver onto the oncoming carriageway, there isthe risk of the driver's own vehicle or of another vehicle being put indanger, for example if there is oncoming traffic on the oncomingcarriageway during the avoidance maneuver, which can be sensed inparticular by the sensor unit.

In order to be able to drive around an obstacle by way of the avoidanceroute, the steering system of the vehicle must be manipulated. However,in the event of the steering actuator device failing, an equivalentstrategy which uses the remaining, still intact vehicle assemblies tominimize damage is expediently followed. To do this, in particular, theassemblies of the vehicle which influence the longitudinal dynamics ofthe vehicle are manipulated, expediently in order to achieve optimumdeceleration with a minimum braking distance.

According to a further preferred embodiment, a communication system, inparticular a graphic display, on which the actual position of thevehicle and the setpoint position which has been determined inaccordance with the avoidance strategy are represented, is provided inthe vehicle. In this way, the driver is informed whether the vehicle isactually on the optimum route—the avoidance path—in the case of ahazard. This provides advantages in particular for a situation in whichthe automatic guidance of the vehicle over the avoidance path does notfunction or does not function completely or else in which such automaticcontrol has not yet been implemented, or not yet implemented completely.In this case, the driver can use the information relating to the actualand setpoint positions for the vehicle which has been communicated tohim, in particular by way of the graphic display, to initiate and carryout steering and braking maneuvers automatically in order to be able toreach, and/or comply with, the displayed setpoint position of thevehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the presentinvention will become more readily apparent from the following detaileddescription of currently preferred configurations thereof when taken inconjunction with the accompanying drawings wherein:

FIG. 1 is a schematic diagram which shows various avoidance routes of avehicle on a road in order to drive around a plurality of obstacles; and

FIG. 2 is a schematic diagram which shows a vehicle having a region ofpossible setpoint trajectories for the continued journey of the vehicletaking into account an obstacle in the path of the vehicle, and thelateral boundaries of the road.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a vehicle 1 on the right-hand half of the carriagewayof a road 2. The vehicle 1 will be assumed to be equipped with anautomatic brake and steering system which permits the vehicle to beautomatically braked and steered as a function of processes, states,events and activities, both outside and inside the vehicle. Thevariables which influence the brake and steering system comprise, inparticular, vehicle state variables (e.g., speed of the vehicle and thesteering speed), vehicle operating variables or vehicle characteristicvariables (e.g., the wheel base), and also signals which originate froma sensor unit and by way of which the ambient conditions can be detected(e.g., obstacles on the carriageway or at the edge of the carriageway orweather-related influences). The sensor unit forms a component of thebrake and steering system which is also assigned a control unit in whichactuation signals can be generated as a function of the vehicle statevariables and the ambient conditions. By way of signal transmissiondevices, these actuation signals are fed to various actuator devices forsetting the vehicle brake and/or the vehicle steering system, ifappropriate also to further assemblies which influence the state of thevehicle, in particular the ignition and injection of the internalcombustion engine of the vehicle.

In the case of an obstacle which blocks the path of the vehicle or atleast lies with an inadequate safety distance in the path of the vehicleand which can be detected by the sensor unit, according to storedcalculation rules avoidance maneuvers, for avoiding collision with theobstacle or avoiding putting the vehicle at risk are determined in thecontrol unit as a function of the vehicle state variables and theambient conditions.

In the herein-described and illustrated embodiment, there is an obstacle3 lying in the path of the vehicle 1 on the carriageway so that thevehicle 1 has to carry out an avoidance maneuver in order to avoid acollision with the obstacle 3, or to prevent the obstacle 3 fromconstituting a hazard. The obstacle 3, which can be detected by thesensor unit of the brake and steering system of the vehicle 1, forexample by a radar system which is carried along in the vehicle 1,forces the vehicle onto avoidance routes which are to be selected incompliance with additional peripheral conditions, in particular incompliance with safety-related criteria.

In the case of the obstacle 3 located in front of the vehicle 1 in thedirection of travel, two avoidance routes a and b, which lead past theobstacle 3 on the left, and respectively on the right, are considered.In order to avoid an avoidance route which is to be adopted constitutinga further hazard for the vehicle 1, peripheral conditions are predefinedwhich are to be complied with in the selection of the avoidance route.One peripheral condition which is taken into account is in particularthe fact that the avoidance route must not lead onto the oncomingcarriageway, so as to avoid a collision with oncoming traffic. However,this peripheral condition can, if appropriate, be restricted to the factthat an avoidance maneuver onto the oncoming carriageway is prohibitedonly if there is actually oncoming traffic; however, this requirespowerful sensor devices in the vehicle 1 which can look far ahead, andmoreover, further favorable ambient conditions, in particular requires aclear view of the course of the route.

An additional criterion to be taken into account in determining theavoidance route is the curvature of the avoidance route which has to beselected, in particular as a function of the longitudinal speed of thevehicle, in such a way that no unacceptably high lateral accelerationsoccur at the vehicle.

As soon as it is detected in the brake and steering system that there isan obstacle in the current path of the vehicle, avoidance routes aredetermined in accordance with the stored avoidance strategy. Thetheoretically possible avoidance routes lead to the left and right ofthe obstacle, and in the exemplary embodiment two avoidance routes a andb on which the vehicle 1 can theoretically drive around the obstacle 3are shown leading past the obstacle 3 on the left and right. However,the avoidance route a cannot be implemented in the exemplary embodimentowing to a restricting peripheral condition, as this route a leads ontothe oncoming carriageway, which is generally not permitted. The onlypath which avoids the obstacle 3 is the avoidance route b which leadspast the obstacle 3 on the right.

In the brake and steering system, the vehicle 1 will advantageouslycontinuously sense the surroundings, in particular at short cyclicalintervals, and this ambient data recorded by the sensor unit is used todetermine further driving strategies continuously or cyclically, and ifappropriate also carry them out. If no further obstacles or disruptionoccur, the avoidance route is expediently selected in such a way thatthe original lateral position of the vehicle 1 with respect to the edgeof the carriageway is reached again in the lateral direction after thetermination of the avoidance maneuver.

If an avoidance maneuver has to be carried out, the lateral component yof the avoidance path is advantageously calculated—measured from thestart of the avoidance maneuver, as a clothoid in accordance with thefunctiony=∫(v ²(t){dot over (Θ)}(t)t ²)/Ldtas a function of the vehicle longitudinal speed v, the longitudinalspeed {dot over (Θ)}, the wheel base L and the time t. It is to be notedthat, in order to drive around the obstacle reliably, the mini mumlateral component y_(min) of the avoidance path is expedientlydetermined by adding half the obstacle width b_(H) and half the vehiclewidth b_(F) in accordance with the relationshipy _(min)=½(b _(H) +b _(F)),in which, if appropriate, an additional lateral safety distance is to betaken into account.

The longitudinal component x of the avoidance path is determinedaccording to the relationshipx=∫v(t)dtas a function of the vehicle speed v.

As an alternative to the clothoid, the cubic parabola can also beselected as an avoidance function.

In FIG. 1, a further case with a multiplicity of obstacles isillustrated in the path d of the vehicle, starting from a vehicleposition 1′ of the vehicle. In the straight-ahead direction there is anobstacle 4 in the path of the vehicle. A further obstacle 5 lies offsetto the side and at a relatively large distance from the vehicle in thelongitudinal direction, and additional individual obstacles 6 arelocated outside the road 2 at the edge of the path. After the obstacle 4which lies directly on the lane d, the vehicle will determine avoidancemaneuvers or avoidance routes c and e, passing the obstacle 4 on theright and left, respectively, starting from the indicated position 1′.

During the determination of the avoidance route which is to be carriedout last, firstly those alternatives which are incompatible withperipheral conditions which are to be additionally borne in mind areeliminated. The obstacles can be divided, as such peripheral conditions,into hierarchical categories which are evaluated with degrees of risk ofdifferent levels for the driver's own vehicle or else for externalpersons or objects. In this way it is possible for persons who arelocated outside the vehicle in question, for example standing at theedge of the path and are identified by the sensor unit as persons, to beplaced in a category of obstacles with which a collision must be avoidedunder all circumstances. By the division and classification into variouscategories, it is possible to perform presorting among a plurality ofavoidance routes which are determined.

In the embodiment described herein, the obstacle 6 can be concerned withindividual persons so that it is not possible to perform an avoidancemaneuver via the route c.

Further remaining alternatives are—starting from the vehicle position1′—the route d which corresponds to the normal path and leads to acollision with the obstacle 4, as well as the avoidance route e, whichhowever, in due course, would also lead to a collision with the obstacle5 which is further away. As the avoidance route c has definitely beeneliminated, it is necessary to make a selection among the remainingroutes d and e. As a selection criterion, firstly the distance betweenthe current vehicle position 1′ and the obstacles 4 and 5 are determinedin the longitudinal direction x. The distance between the vehicleposition 1′ and the obstacle 4 which is closer is s_(H1), the distancefrom the obstacle 5 which is further away is s_(H2). At the same time,the remaining minimum braking distance s_(B), which is expected to benecessary starting from the current vehicle position 1′ up to a completestandstill of the vehicle in the longitudinal direction x is determinedat the same time in the control unit of the brake and steering system.If the remaining braking distance s_(B) exceeds the distance s_(H1) ands_(H2) which is available for obstacle-free journey as far as theobstacles, and consequently a collision-free avoidance path startingfrom the vehicle position 1′ cannot be found, that avoidance path inwhich the difference between the braking distance s_(B) and the distances_(H1) or s_(H2) from the respective obstacle 4 or 5 is smallest is thenselected as a criterion for the selection among the remaining routes dand e. Owing to the larger longitudinal distance between the obstacle 5and the current vehicle position 1′, this difference which is referredto by Δs₁ and Δs₂ is smallest for the obstacle 5, and accordingly theavoidance route e is selected. Owing to the larger distance from theobstacle 5, the vehicle will be decelerated to a lower speed than whenapproaching the obstacle 4 on the route d, and the damage in the eventof an impact against the obstacle 5 will be less than the damage in theevent of an impact against the closer obstacle 4.

After the vehicle has adopted the avoidance route e starting from theposition 1′, further avoidance routes are investigated continuously incyclical intervals. In the process, further alternatives may be found,for example an avoidance route f, which can however only be carried outif no additional peripheral conditions are infringed or if the route fis placed in a classification category which is the same, or preferablymore favorable, in terms of safety aspects than the route e which hasbeen adopted at the particular time. However, in the exemplaryembodiment, the route f is not a feasible alternative to the route e asthe route f leads onto the oncoming carriageway.

In the event of a failure of the steering actuation device which bringsabout automatic steering, it is not possible to perform an automaticlateral avoidance maneuver and drive around an obstacle. In this case,the vehicle longitudinal dynamics are expediently influenced inaccordance with a stored equivalent strategy, in particular maximumdeceleration is generated by acting on the vehicle brake and/or theengine in order to brake the vehicle as quickly as possible to astandstill after the detection of the failure of the steering actuationdevice and after an obstacle has been detected. This strategy can alsobe applied generally if a steering actuation device is not present inthe vehicle.

In a further currently preferred embodiment, a communication system, inparticular a graphic communication system for representing the actualvehicle position and setpoint position which is to be adopted inaccordance with the avoidance route is provided in the vehicle. Inparticular, if the automatic adoption of an avoidance route is notpossible, or not entirely possible, as a result of an impaired functionof the brake and steering system, the driver is provided, by way of thecommunication system, with sufficient information on the optimum drivingroute which can be correspondingly adopted manually by the driver.

In a further embodiment, a memory unit in which data of the brake andsteering system can be stored permanently or temporarily is assigned tothe brake and steering system. Both the data used as the basis fortriggering the automatic brake and/or steering system and the datagenerated by the brake and steering system is expediently stored inorder, subsequently, to be able to determine and assess both thedatabase which the brake and steering system uses as a basis forgenerating actuation signals, and the generated actuation signalsthemselves and/or their effect. In particular, both setpoint variablesand actual variables can be stored in the memory unit. The behavior ofthe brake system and the occurrence of a fault in the brake and steeringsystem can be reconstructed on the basis of the stored data. Inaddition, decisions of the driver which run counter to decisions orproposals of the brake and steering system can subsequently be checkedfor correctness. The data can be stored in the memory unit for a limitedtime or for an unlimited time. In the case of a chronological limitationwhich is predefined to a specific storage interval, after the first passof the storage interval, data from the elapsed storage interval isadvantageously continuously overwritten with subsequent data.

It may also be advantageous to provide, in the vehicle, aposition-determining system for determining the instantaneous absoluteposition, for example a satellite-supported position-determining systemGPS. In conjunction with an electronic road map which is to be carriedalong in the vehicle and which contains information in digitized formrelating to the topography of the road which is currently being drivenon and the surroundings, a navigation system with which additionalcriteria can be taken into account in the selection of the avoidanceroute is obtained in that topographical or topological conditions whichresult from the electronic map are taken into account by the sensor unitcarried along in the vehicle, independently of the detection ofobstacles. In this way, the absolute vehicle position is expedientlydetermined using the position-determining system and transmitted intothe electronic road map from which the profile of the road and inparticular the lateral boundaries of the road as well as fixed obstaclesare known, which is to be taken into account as a peripheral condition,in the sense of a region which is not to be driven through or only to bedriven through under special circumstances, in the determination of theavoidance route. The road profile can, if appropriate, also be stored ina three-dimensional form and taken into account in the selection of thesuitable route as a spatial curve.

FIG. 2 depicts a vehicle 1 which has an automatic brake and steeringsystem, on a carriageway 2. The vehicle 1 is capable of using its sensorsystem to detect an obstacle 3 in front of it on the carriageway 2 andof determining an avoidance route which bypasses the obstacle, and ofautomatically following the selected avoidance route by acting on thesteering assemblies and the brake assemblies as well as, if appropriate,also other engine assemblies. The vehicle 1 also has a navigation systemwhich comprises a position-determining system for determining theinstantaneous absolute position of the vehicle as discussed above, andan electronic road map in which the topography of the road currentlybeing driven on as well as the surroundings are stored. Theposition-determining system is expediently a satellite-supportedlocating system.

By determination of the absolute position of the vehicle 1 andcomparison with the electronic road map, it is contemplated to take intoaccount topological conditions and particular features in the currentprofile of the road and the surroundings as additional peripheralconditions in the determination of the optimum avoidance route. Bytaking into account the topological route profile as well as theobstacle 3 on the carriageway 2, an area 7 which contains a region whichthe vehicle 1 is permitted to be in can be determined, with all itspossible avoidance routes or trajectories which the vehicle I cantheoretically follow in order both to be able to avoid the obstacle 3and also maintain a sufficient distance from the lateral boundaries 8 ofthe carriageway or other obstacles which can be obtained from the roadmap.

From knowledge of the profile of the route which is known from using thenavigation system, peripheral conditions can be taken into account indetermining and executing the movement of the vehicle both with respectto position and also, if appropriate, with respect to speed and/oracceleration. As a result, a predictive, automatic method of driving isnow possible because the two-dimensional, or if appropriate also thethree-dimensional profile of the route can be taken into account withrespect to positive and negative acceleration forces which act on thevehicle in the longitudinal and lateral directions.

On the area 7 of the permitted vehicle movement, an individual area lineor spatial line or trajectory is determined as a setpoint value profileor as a setpoint trajectory for the vehicle. The selection of thesetpoint trajectory can in turn be made taking into account optimizationcriteria or peripheral conditions, and in the simplest approximationthat trajectory which lies in the center of the area 7 of thepermissible vehicle movement is selected as the setpoint trajectory.

Anchor points 10 which serve as a mathematical location for a dynamicvehicle model which is simulated in the brake and steering system can beset on the setpoint trajectory 9. From this dynamic vehicle model,vehicle variables which reflect the driving behavior of the real vehiclecan be determined. If it is decided in the simulation that the vehiclecan get into a critical situation when the current state is maintained,interventions can be made steering system in order to avoid such amethod situation, for example the vehicle speed can be reduced and/orthe setpoint trajectory which yields a more favorable profile, in termsof the hazardous vehicle state, of the accelerations and forces actingon the vehicle, can be redetermined.

1. Automatic brake and steering system for a vehicle, comprising asensor unit configured to sense vehicle state variables, vehiclecharacteristic variables and ambient conditions, a control unitconfigured to generate actuation signals as a function of the sensedvehicle state variables and the ambient conditions, actuation signalsbeing feedable to actuation devices in the vehicle to operate thevehicle brake and the vehicle steering system, the system beingconfigured to determine a distance between a current vehicle positionand an obstacle, to automatically drive along an avoidance path fordriving around the obstacle in accordance with a stored avoidancestrategy, to determine obstacle distances between the current vehicleposition and each further obstacle when further obstacles are located infront of the vehicle as well as a minimum distance needed to bring thevehicle to a standstill, to determine differences between said minimumdistance and said obstacle distances, to select an alternative avoidancepath with a smallest difference between said minimum distance andobstacle distances, and to operate the vehicle brake and the vehiclesteering system to follow the alternative avoidance path selected. 2.Brake and steering system according to claim 1, wherein the alternativeavoidance path selected is that avoidance path which does not lead to anoncoming carriageway.
 3. Brake and steering system according to claim 2,wherein the sensor unit is configured to sense peripheral conditionswhich describe characteristic features of the surroundings, and thesystem is configured to take the sensed peripheral conditions intoaccount in the avoidance strategy.
 4. Brake and steering systemaccording to claim 2, wherein the system divides the further obstaclesinto categories, with avoidance paths which lead to a collision with adefined category of obstacles being eliminated in the avoidancestrategy.
 5. Brake and steering system according to claim 1, furthercomprising a memory unit operatively associated with the brake andsteering system, such that at least certain data for the automatictriggering of a brake and/or steering process and/or at least certaindata generated by the brake and steering system are storable in thememory unit.
 6. Brake and steering system according to claim 5, whereinat least certain data are stored in the memory unit only for a limited,predefined period of time before the vehicle last comes to a standstill.7. Brake and steering system according to claim 5, wherein certain dataare stored in the memory unit without time restriction.
 8. Brake andsteering system according to claim 7, wherein at least certain data arestored in the memory unit only for a limited, predefined period of timebefore the vehicle last comes to a standstill.
 9. Brake and steeringsystem according to claim 1, wherein an electronic road map is providedand contains digitized data relating to road topography being drivenalong at a particular time, and road surroundings.
 10. Brake andsteering system according to claim 9, wherein a position-determiningsystem is provided for determining an instantaneous position of thevehicle.
 11. Brake and steering system according to claim 9, wherein theinstantaneous vehicle position is enterable into the electronic roadmap, and peripheral conditions which are to be taken into account in theavoidance strategy are generatable from the position of the vehicle onthe road map.
 12. Brake and steering system according to claim 1,wherein the system divides the further obstacles into categories, withavoidance paths which lead to a collision with a defined category ofobstacles being eliminated in the avoidance strategy.
 13. Brake andsteering system according to claim 12, wherein the sensor unit isconfigured to sense peripheral conditions which describe characteristicfeatures of the surroundings, and the system is configured to take thesensed peripheral conditions into account in the avoidance strategy. 14.Brake and steering system according to claim 1, wherein, in case of afailure of a steering actuating device, an assembly which influencesvehicle longitudinal dynamics is employed in the system in accordancewith a predefined equivalent strategy.
 15. Brake and steering systemaccording to claim 14, wherein the system is configured to deceleratethe vehicle with maximum deceleration by activating at least one of avehicle brake and an engine brake.
 16. Brake and steering systemaccording to claim 1, wherein a position-determining system is providedfor determining an instantaneous position of the vehicle.
 17. Brake andsteering system according to claim 16, wherein the position-determiningsystem is a satellite-supported system.
 18. Brake and steering systemaccording to claim 1, wherein the sensor unit is configured to senseperipheral conditions which describe characteristic features of thesurroundings, and the system is configured to take the sensed peripheralconditions into account in the avoidance strategy.
 19. Brake andsteering system according to claim 1, wherein the vehicle is providedwith a graphic display for representing an actual vehicle position and asetpoint position determined in accordance with the avoidance strategy.20. Automatic brake and steering method for a vehicle, comprisingsensing vehicle state variables, vehicle characteristic variables andambient conditions, generating actuation signals as a function of thesensed vehicle state variables and the ambient conditions, determining adistance between a current vehicle position and an obstacle, feeding theactuation signals to actuation devices in the vehicle to operate thevehicle brake and the vehicle steering system so as to automaticallydrive along an avoidance path for driving around the obstacle inaccordance with a stored avoidance strategy, determining obstacledistances between the current vehicle position and each further obstaclewhen further obstacles are located in front of the vehicle as well as aminimum distance needed to bring the vehicle to a standstill,determining differences between said minimum distance and said obstacledistances, selecting an alternative avoidance path with a smallestdifference between said minimum distance and obstacle distances, andoperating the vehicle brake and the vehicle steering system to followthe alternative avoidance path selected.
 21. Brake and steering methodaccording to claim 20, further comprising storing at least certain datafor at least one of the automatic triggering of a brake, the steeringprocess and brake and steering system generated data.
 22. Brake andsteering method according to claim 21, wherein certain data are storedin the memory unit without time restriction.
 23. Brake and steeringmethod according to claim 22, wherein at least certain data are storedonly for a limited, predefined period of time before the vehicle lastcomes to a standstill.
 24. Brake and steering method according to claim21, wherein at least certain data are stored in the memory unit only fora limited, predefined period of time before the vehicle last comes to astandstill.
 25. Brake and steering method according to claim 20, whereinthe alternative avoidance path selected is that avoidance path whichdoes not lead to an oncoming carriageway.
 26. Brake and steering methodaccording to claim 25, further comprising sensing peripheral conditionswhich describe characteristic features of the surroundings, and takinginto account the sensed peripheral conditions in the avoidance strategy.27. Brake and steering method according to claim 25, further comprisingdividing the further obstacles into categories, with avoidance pathswhich lead to a collision with a defined category of obstacles beingeliminated in the avoidance strategy.
 28. Brake and steering methodaccording to claim 20, further comprising dividing the further obstaclesinto categories, with avoidance paths which lead to a collision with adefined category of obstacles being eliminated in the avoidancestrategy.
 29. Brake and steering method according to claim 28, furthercomprising sensing peripheral conditions which describe characteristicfeatures of the surroundings, and taking into account the sensedperipheral conditions in the avoidance strategy.
 30. Brake and steeringmethod according to claim 20, further comprising, in case of a failureof a steering actuating device, influencing vehicle longitudinaldynamics in accordance with a predefined equivalent strategy.
 31. Brakeand steering method according to claim 30, further comprisingdecelerating the vehicle with maximum deceleration by activating atleast one of a vehicle brake and an engine brake.
 32. Brake and steeringmethod according to claim 20, further comprising sensing peripheralconditions which describe characteristic features of the surroundings,and taking into account the sensed peripheral conditions in theavoidance strategy.
 33. Brake and steering method according to claim 20,further comprising determining an instantaneous position of the vehicle.34. Brake and steering method according to claim 20, further comprisingproviding digitized data relating to road topography being driven alongat a particular time, and road surroundings.
 35. Brake and steeringmethod according to claim 20, further comprising graphically displayinga representation of an actual vehicle position and a setpoint positiondetermined in accordance with the avoidance strategy.
 36. Automaticbrake and steering system for a vehicle, comprising a sensor unitconfigured to sense vehicle state variables, vehicle characteristicvariables and ambient conditions, a control unit configured to generateactuation signals as a function of the sensed vehicle state variablesand the ambient conditions, actuation signals being feedable toactuation devices in the vehicle to operate the vehicle brake and thevehicle steering system, the system being configured to determine adistance between a current vehicle position and an obstacle as well asan expected braking distance in order to stop the vehicle when theobstacle is in the path of the vehicle, and to automatically drive alongan avoidance path for driving around the obstacle in accordance with astored avoidance strategy, and, in the event of a further obstacle lyingin the avoidance path, the avoidance strategy is applied again tocalculate an alternative avoidance path, such that, in the event of acollision-free avoidance path not being available, the alternativeavoidance path is one on which a difference between a minimum distanceneeded to bring the vehicle to a standstill and a remaining distancefrom each obstacle on the respective avoidance path is the shortest isselected, wherein a width of the obstacle in a lateral direction of thevehicle is determined, and a minimum lateral component of the avoidancepath is determined by adding half of the width of the obstacledetermined and half of a vehicle width.
 37. Brake and steering systemaccording to claim 36, wherein the sensor unit is configured to senseperipheral conditions which describe characteristic features of thesurroundings, and the system is configured to take the sensed peripheralconditions into account in the avoidance strategy.
 38. Brake andsteering system according to claim 36, wherein the system divides theobstacles into categories, with the avoidance paths which lead to acollision with a defined category of obstacles being eliminated in theavoidance strategy.
 39. Automatic brake and steering method for avehicle, comprising sensing vehicle state variables, vehiclecharacteristic variables and ambient conditions, generating actuationsignals as a function of the sensed vehicle state variables and theambient conditions, determining a distance between a current vehicleposition and an obstacle as well as an expected braking distance inorder to stop the vehicle when the obstacle is in the path of thevehicle, feeding the actuation signals to actuation devices in thevehicle to operate the vehicle brake and the vehicle steering system soas to automatically drive along an avoidance path for driving around theobstacle in accordance with a stored avoidance strategy, and, in theevent of a further obstacle lying in the avoidance path, the avoidancestrategy is applied again to calculate an alternative avoidance path,whereby, in the event of a collision-free avoidance path not beingavailable, the alternative avoidance path is one on which a differencebetween a minimum distance needed to bring the vehicle to a standstilland a remaining distance from each obstacle on the respective avoidancepath is the shortest is selected, determining a width of the obstacle ina lateral direction of the vehicle, and determining a minimum lateralcomponent of the avoidance path by adding half of the width of theobstacle determined and half of a vehicle width.
 40. Brake and steeringmethod according to claim 39, further comprising sensing peripheralconditions which describe characteristic features of the surroundings,and taking into account the sensed peripheral conditions in theavoidance strategy.
 41. Brake and steering method according to claim 39,further comprising dividing the obstacles into categories, with theavoidance paths which lead to a collision with a defined category ofobstacles being eliminated in the avoidance strategy.
 42. Automaticbrake and steering system for a vehicle, comprising a sensor unitconfigured to sense vehicle state variables, vehicle characteristicvariables and ambient conditions, a control unit configured to generateactuation signals as a function of the sensed vehicle state variablesand the ambient conditions, actuation signals being feedable toactuation devices in the vehicle to operate the vehicle brake and thevehicle steering system, the system being configured to determine adistance between a current vehicle position and an obstacle as well asan expected braking distance in order to stop the vehicle when theobstacle is in the path of the vehicle, and to automatically drive alongan avoidance path for driving around the obstacle in accordance with astored avoidance strategy, and, in the event of a further obstacle lyingin the avoidance path, the avoidance strategy is applied again tocalculate an alternative avoidance path, such that, in the event of acollision-free avoidance path not being available, the alternativeavoidance path is one on which a difference between a minimum distanceneeded to bring the vehicle to a standstill and a remaining distancefrom each obstacle on the respective avoidance path is the shortest isselected, wherein a lateral component y of the avoidance path isdetermined as follows:y=∫(v ²(t){dot over (Θ)}(t)t ²)/Ldt where v is the vehicle speed, t istime, {dot over (Θ)} is steering speed, and L is the wheel base. 43.Automatic brake and steering method for a vehicle, comprising sensingvehicle state variables, vehicle characteristic variables and ambientconditions, generating actuation signals as a function of the sensedvehicle state variables and the ambient conditions, determining adistance between a current vehicle position and an obstacle as well asan expected braking distance in order to stop the vehicle when theobstacle is in the path of the vehicle, feeding the actuation signals toactuation devices in the vehicle to operate the vehicle brake and thevehicle steering system so as to automatically drive along an avoidancepath for driving around the obstacle in accordance with a storedavoidance strategy, and, in the event of a further obstacle lying in theavoidance path, the avoidance strategy is applied again to calculate analternative avoidance path, whereby, in the event of a collision-freeavoidance path not being available, the alternative avoidance path isone on which a difference between a minimum distance needed to bring thevehicle to a standstill and a remaining distance from each obstacle onthe respective avoidance path is the shortest is selected, where alateral component y of the avoidance path is determined as follows:y=∫(v ²(t){dot over (Θ)}(t)t ²)/Ldt where v is the vehicle speed, t istime, {dot over (Θ)} is steering speed, and L is the wheel base.